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Process For Preparation Of Adipic Acid - Patent 6235932


The present invention relates to process for the formation of adipic acid from cyclohexane and the adipic acid thus formed.The invention resides in the use of pure molecular oxygen as an oxidant which results in providing higher selectivity towards the formation of adipic acid.The object of the invention is to increase the selectivity and the yield of adipic acid from cyclohexane. The product selectivities using the process of the present invention have been found to be at least 5% higher than the maximum attainableusing the hitherto known conventional processes. The process of the present invention employs use of preactivated catalyst in the reactor for carrying out the reaction.BACKGROUND OF THE INVENTIONAdipic acid is widely used in the manufacture of polyesters, polyamides, plasticizers and the like. Conventionally adipic acid is known to be produced by two step oxidation of cyclohexane. In the first step KA oil is produced from cyclohexaneby air oxidation which is then oxidized by nitric acid to dicarboxylic acids such as adipic acid, glutaric acid and succinic acid. This process suffers from various disadvantages, especially relating to low conversion per pass of the hydrocarbon in thefirst step (3-8%), leading to large recycle; use of nitric acid in the second step leading to NOx pollution; and formation of byproducts like lactones which pose difficulties in the downstream use of adipic acid.In order to overcome drawbacks in the two step oxidation process, one step oxidation of cyclohexane has been tried over the years. Air is used as an oxidant in one step oxidation of cyclohexane. The catalysts mostly used in the oxidation ofcyclohexane are cobalt and its mixture with other metals like iron. In the conventional methods, in-situ activation of the catalyst from cobaltous to cobaltic state is carried out with the help of activators like aldehydes and ketones.The earlier known patents have divulged the use of any oxygen containing gas, however, the know

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